Cotton Response to Simulated Auxin Herbicide Drift Using Standard and Ultra-low Carrier Volumes

Field experiments were conducted in Citra, FL, and Tifton, GA, to evaluate simulated drift of dicamba and 2,4-D on cotton. Drift applications were made at the sixth leaf and first square growth stages using variable and constant carrier volumes and the same herbicide rate. Drift applied using variable carrier volumes were proportionally reduced with the herbicide rate while drift applied at constant carrier volumes were all made at 140 L ha-1, regardless of herbicide rate. At 21 DAT, dicamba applied at variable carrier volumes reduced cotton heights 8% [from nontreated check (NTC)] compared to no change in height with dicamba applied at constant carrier volumes. The same effect was seen with 2,4-D applied at first square where variable carrier volumes decreased cotton heights 18% (from NTC) compared to 2% at 140 L ha-1. Cotton yields were reduced to 70% of NTC when dicamba was applied at sixth leaf at variable carrier volumes compared to 87% at constant carrier volumes. The same response was seen with 2,4-D applied at sixth leaf where variable carrier volumes reduced cotton yields to 19% of NTC compared to 32% at constant carrier volumes. Cotton injury, height, boll production, and yield were all affected by drift carrier volume. When simulating herbicide drift in the future, it is critical to use variable carrier volumes for application as constant carrier volumes have shown to decrease the amount of plant injury observed. Nomenclature: 2,4-D; dicamba; cotton (Gossypium hirsutum L.) Experimentos de campo fueron realizados en Citra, Florida y Tifton, Georgia, para evaluar el efecto de la deriva simulada de dicamba y 2,4-D sobre el algodón. Se realizaron aplicaciones de deriva en los estadios de sexta hoja y de primer cuadrado usando volúmenes variables y constantes y la misma dosis del herbicida. La deriva aplicada usando volúmenes variables fue proporcionalmente reducida con la dosis del herbicida mientras que las derivas aplicadas a volúmenes constantes fueron todas hechas a 140 L ha−1, sin importar la dosis del herbicida. A 21 DAT, dicamba aplicado con volúmenes variables redujo la altura del algodón 8% (con base en el testigo sin tratamiento [NTC]) en comparación con la ausencia de cambio en la altura con dicamba aplicado con volúmenes constantes. El mismo efecto se vio con 2,4-D aplicado en el estadio del primer cuadrado cuando los volúmenes variables disminuyeron la altura del algodón 18% (con base en NTC) en comparación con 2% a 140 L ha−1. Los rend